Generating sample error coefficients

• US 8,548,804 B2
• Filed: 10/19/2007
• Issued: 10/01/2013
• Est. Priority Date: 11/03/2006
• Status: Active Grant

• Current Assignee: Psytechnics Ltd. (NetScout Systems Incorporated)
• Original Assignee: Psytechnics Ltd. (NetScout Systems Incorporated)
• Inventors: Barrett, Paul, Maifait, Ludovic
• Primary Examiner(s): Desir, Pierre-Louis
• Assistant Examiner(s): KOVACEK, DAVID M
• Application Number:
  US11/874,967
• Publication Number:
  US 20080106249A1
• Time in Patent Office: 2,174 Days
• Field of Search: 704200-218, 704/224, 704236-240, 704/270.1, 704E19001-E19049, 704E21001-E21002
• US Class Current: 704/236
• CPC Class Codes: G10L 19/09 Long term prediction, i.e. removing periodical redundancies, e.g. by using adaptive codebook or pitch predictor
• CPC Class Codes: G10L 21/04 Time compression or expansion
• CPC Class Codes: G10L 25/69 for evaluating synthetic or decoded voice signals

Abstract

This invention relates to generation of a sample error coefficient suitable for use in an audio signal quality assessment system. The invention provides a method of determining a sample error coefficient between a first signal and a similar second signal comprising the steps of: determining a first periodicity measure from the first signal; determining a second periodicity measure from the second signal; generating a ratio in dependence upon said first periodicity measure and said second periodicity measure; and determining a sampling rate error coefficient in dependence upon said ratio.

Claims

1. A method of determining a sample error coefficient between a first signal and a similar second signal comprising the steps of:

receiving the second signal via a communications channel, the second signal being a transmitted version of the first signal;

dividing the first signal into a first plurality of segments;

dividing the second signal into a second plurality of segments;

determining a first periodicity measure of one of the first plurality of segments and a second periodicity measure of one of the second plurality of segments;

determining that the first periodicity measure and the second periodicity measure exhibit similarity which exceeds a similarity threshold;

determining a third periodicity measure of another of the first plurality of segments and a fourth periodicity measure of one of the second plurality of segments;

determining that the third periodicity measure and the fourth periodicity measure exhibit similarity which exceeds the similarity threshold;

generating a first ratio in dependence upon said first periodicity measure and said second periodicity measure and a second ratio in dependence upon said third periodicity measure and said fourth periodicity measure;

determining a first segment sample rate error coefficient based on the first ratio;

determining a second segment sample rate error coefficient based on the second ratio; and

determining a sampling rate error coefficient based on both the first and second segment sample rate error coefficients.

2. A method according to claim 1, in which the first signal is a first known signal to be transmitted via the communications channel and the second signal is a first received signal, being a possibly degraded version of said first known signal, received via said communications channel.

3. A method according to claim 2, in which the first known signal is a signal comprising a tone.

4. A method according to claim 3, in which the first known signal is a signal comprising a plurality of tones.

5. A method according to claim 1, in which the steps of determining the first periodicity measure and the second periodicity measure comprise the step of determining the pitch period of each signal.

6. A method according to claim 5, in which the pitch period is determined in dependence upon the position of a peak in the autocorrelation function of each signal.

7. A method according to claim 1, in which the determining the first periodicity measure and the second periodicity measure depends upon the frequency of one or more peaks in the Fourier Transform of each signal.

8. A method according to claim 1, in which the first plurality of segments and second plurality of segments comprise segments having a periodic component.

9. A method according to claim 1, in which the first segment sample rate error coefficient and second segment sample rate error coefficient are used to form a histogram and the sampling rate error coefficient is determined by selecting a value from a histogram bin having the greatest number of coefficients.

10. A method according to claim 9, in which said value is selected by generating an average of the values in the histogram bin having the greatest number of coefficients.

11. A method according to claim 1, in which sample rates of the first plurality of segments and second plurality of segments are used to form a histogram and the sampling rate error coefficient is determined by interpolating between multiple histogram bins.

12. A method according to claim 1, further comprising:

receiving the second signal, the second signal being a possibly degraded version of the first signal, via said communications channel;

resampling the second signal in dependence upon said sampling rate error coefficient to generate a resampled signal;

comparing the first signal to the resampled signal and generating an error pattern; and

generating a quality measure of the communications channel based on the comparison of the first signal to the resampled signal and the generated error pattern.

13. A method according to claim 12 in which resampling the second signal is performed using a truncated sin(x)/x transfer function.

14. A non-transitory computer readable storage medium storing executable computer program instructions for determining a sample error coefficient between a first signal and a similar second signal, the instructions performing steps comprising:

receiving the second signal via a communications channel, the second signal being a transmitted version of the first signal;

dividing the first signal into a first plurality of segments;

dividing the second signal into a second plurality of segments;

determining a first periodicity measure of one of the first plurality of segments and a second periodicity measure of one of the second plurality of segments;

determining that the first periodicity measure and the second periodicity measure exhibit similarity which exceeds a similarity threshold;

determining a third periodicity measure of another of the first plurality of segments and a fourth periodicity measure of one of the second plurality of segments;

determining that the third periodicity measure and the fourth periodicity measure exhibit similarity which exceeds the similarity threshold;

generating a first ratio in dependence upon said first periodicity measure and said second periodicity measure and a second ratio in dependence upon said third periodicity measure and said fourth periodicity measure;

determining a first segment sample rate error coefficient based on the first ratio;

determining a second segment sample rate error coefficient based on the second ratio; and

determining a sampling rate error coefficient based on both the first and second segment sample rate error coefficients.

15. The computer readable storage medium of claim 14, wherein determining the first periodicity measure and the second periodicity measure depends upon the frequency of one or more peaks in the Fourier Transform of each signal.

16. The computer readable storage medium of claim 14, wherein the first plurality of segments and second plurality of segments comprise segments having a periodic component.

17. The computer readable storage medium of claim 14, wherein the first segment sample rate error coefficient and second segment sample rate error coefficient are used to form a histogram and the sampling rate error coefficient is determined by selecting a value from a histogram bin having the greatest number of coefficients.

18. The computer readable storage medium of claim 14, wherein sample rates of the first plurality of segments and second plurality of segments are used to form a histogram and the sampling rate error coefficient is determined by interpolating between multiple histogram bins.

19. The computer readable storage medium of claim 14, the steps further comprising:

receiving the second signal, the second signal being a possibly degraded version of the first signal, via said communications channel;

resampling the second signal in dependence upon said sampling rate error coefficient to generate a resampled signal;

comparing the first signal to the resampled signal and generating an error pattern; and

generating a quality measure of the communications channel based on the comparison of the first signal to the resampled signal and the generated error pattern.